Improve ExtractWorkflowNameFromFile hot-path parsing to recover benchmark regression

[Copilot]

BenchmarkExtractWorkflowNameFromFile regressed materially versus historical baseline despite low allocations. This change reduces per-line parsing overhead in the workflow title scanner while preserving existing parsing behavior for whitespace-tolerant markdown/frontmatter inputs.

• Parser hot path simplification

  • Updated fastParseTitleFromReader to check raw scanned bytes first for:
    • frontmatter delimiters (---)
    • H1/H2/H3 prefixes
  • Falls back to trimmed-line checks only when needed, avoiding unconditional TrimSpace/prefix work on every line.

• Behavior-preserving helper extraction

  • Added focused helpers to make branch logic explicit and cheap:
    • isFrontmatterDelimiter([]byte)
    • extractHeadingTitle([]byte) (string, bool)

• Edge-case coverage for whitespace-tolerant parsing

  • Added a targeted test case covering:
    • frontmatter delimiters with surrounding whitespace
    • indented H1 title extraction

if title, ok := extractHeadingTitle(line); ok {
	return title, nil
}
if trimmed := bytes.TrimSpace(line); !bytes.Equal(trimmed, line) {
	if title, ok := extractHeadingTitle(trimmed); ok {
		return title, nil
	}
}

[github-actions]

Thanks for documenting the benchmark regression and the intended parser optimization clearly. The core change is on-topic, but this PR is not focused yet because it also updates a very large set of .lock.yml workflow artifacts unrelated to the parser hot path, which makes review harder.

Please split this into a narrowly scoped PR that contains only the parser/test changes, or clearly justify why the lockfile churn is required for this change.

You are updating PR #45225 for gh-aw.

Goal: make the PR tightly focused.

Tasks:
1. Remove unrelated `.github/workflows/*.lock.yml` changes from this PR unless they are strictly required by the parser change.
2. Keep only the source/code/test changes directly related to `ExtractWorkflowNameFromFile` performance and behavior preservation.
3. Ensure the PR description explains:
   - what regressed,
   - why this implementation fixes it,
   - what test coverage was added.
4. Recalculate the diff so reviewers can evaluate one concern only.

Constraints:
- Do not add new dependencies.
- Preserve or improve the existing targeted test coverage.
- Prefer a small, reviewable diff.

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